Auxiliary valve stem seal

ABSTRACT

An auxiliary valve stem seal which permits removal and replacement of the main stem packing. An elastomeric ring around the stem inward of the main packing is normally of an inner diameter larger than the stem so that it is ineffective as a seal. A pressure fluid is selectively introduced around the seal ring, causing it to deform to a smaller diameter and seal around the stem. When the main stem packing is repaired and replaced, the sealing pressure fluid is relieved to render the auxiliary seal ineffective.

United States Patent [72] Inventors gllrvln [55] References and utro y;UN Roger L. Rlpert, Concord, both of, Cll". [TED STATES PATENTS [2]]App.. No. 873,034 2,625,413 l/l953 Christensen 277/l87 [22] Filed00.31.1969 2,943,874 7/l960 Valdiet al. 277/343 [45] Patented Au ".19713,096,070 7/1963 Wolfensperger 277/59 X {73] Assign Gm" VIM! dkeguhmrcompany 3,400,937 I0/l968 Crankshaw 277/34 Oakland, Cnlil.FOREIGN PATENTS 820,020 9/1959 Great Britain 277/343 PrimaryExaminer-Samuel B. Rothberg AnornyMelvin R. Stidham [54] AUXILIARY VALVESTEM SEAL ABSTRACT: An auxiliary valve stem seal which permits schhmsnnwlng gs. removal and replacement of the main stem packing. Anelastomeric ring around the stem inward of the main packing [52] [1.8.CI 277/9, is normally of an inner diameter larger than the stem so thatit 277/34, 25l/2l4 is ineffective as a seal A pressure fluid isselectively in- [5|] lnt.Cl Fl6j9/00, troduced around the seal ring,causing it to deform to a F02fl1/00 smaller diameter and seal around thestem. When the main [50] Field 0! Search 277/9, 34, stem packing isrepaired and replaced, the sealing pressure 343, 59, I74; 251/214;l37/3l5 fluid is relieved to render the auxiliary seal ineffective.

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SHEET 3 OF 3 .ElEi-El- 46 INVENTOR. MARVIN 6 COMbES FIB-6;- By 0661? L.k/PfkT ATT'OENE'Y AUXILIARY VALVE STEM SEAL BACKGROUND OF THE INVENTIONThis invention relates to an auxiliary valve stem seal and, moreparticularly, to a seal which may be activated selectively to sealaround the valve stem and thereby enable the removal and replacement ofthe main stem packing while the valve is still in the line.

In the conventional gate, globe, angle and similar valves, a seal isprovided in the bonnet around the valve stem in order to retain pressurewithin the valve body. The valve stem packing may comprise a resilientmaterial held against the stem by a retainer or simply a bushing withsuitable seal rings. In most cases, the stem seal cannot be removed andreplaced with the valve in the line under pressure. Some valves dopermit repacking or replacing the stem seal while the valve is underpressure, but there is a further limitation in such valves in that therepacking is possible only with the valve in open position. In suchvalves, there is a smoothly finished shoulder on the stem or a portionof the top of the valve closure member is finished, to provide ametalto-metal seal in the bonnet when the valve stem is raised to itsfully open position.

OBJECTS OF THE INVENTION It is an object of this invention to provide anauxiliary valve stem seal which may be activated selectively to permitremoval and replacement of the main stem seal means.

It is a further object of this invention to provide an auxiliary valvestem seal which may be activated to enable repacking the stern in anyposition thereof.

Other objects and advantages of the invention will become apparent fromthe detailed description to follow when read in conjunction with theaccompanying drawing.

BRIEF DESCRIPTION OF THE INVENTION In a preferred embodiment of thisinvention, a recess is provided around the bonnet opening inward of themain valve stem packing, and an elastomeric ring in the recess issqueezed axially to seal across the recess in an axial direction. Theseal ring normally has an inner diameter larger than the stem so that itsurrounds it freely and does not seal around it. A duct leads into therecess behind the seal ring from a source of relatively high-pressurefluid, as for example, the valve body or the upstream hub. A three-waycontrol valve means normally closes the duct to pressure fluid, but mayselectively be opened to direct the high-pressure fluid behind the sealring. With the seal ring sealing across the recess, the pressure drivesit radially inward around its circumference to squeeze around the stem,sealing off the bonnet. Then, the main packing may be removed andserviced and, when it is replaced, the control valve is operated, firstto shut off the pressure source and then to relieve the auxiliary sealto atmosphere. The relief passage may subsequently be closed when theseal ring expands to its normal diameter.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is an enlarged partial sectionview ofa valve bonnet and stem embodying features of this invention;

FIG. IA is a further section view of the valve bonnet with the auxiliaryseal activated;

FIG. 2 is a plan view ofa valve body illustrating another embodiment ofthis invention; and

FIGS. 3 and 4 are enlarged partial section views of valve bonnetconstructions with other embodiments of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The Embodiment of FIG. 1Referring more particularly to FIG. 1, there is illustrated a valve bodywith a conventional bonnet having an opening l2 therethrough toaccommodate a valve stem 14. A stern bushing 15 carries an outer O-ring16 which seals between the stern bushing 15 and the counterbore wall 17,and one or more inner O-rings 18 to seal around the stem 14. A flange 19at the upper end of the valve body stem is provided for attachment of asuitable valve-operating device (not shown).

Situated below the stem packing 15 is a recess 20 which accommodates anO-ring 22 or similar resilient seal means. The resilient seal is of athickness in the axial direction relative to the recess 20 such that theseal ring will be squeezed between the sidewalls of the recess. At thesame time, it is of a radius such that it is completely accommodatedwithin the recess 20 and out of contact with the valve stem 12 while inits normal configuration shown in FIG. I. That is the inner diameter ofthe seal ring 22 is sufficiently greater than the outer diameter of thevalve stem 14 that it is completely ineffective to seal off any fluidflow that may occur in the clearances between the bonnet opening 12 andthe valve stem 14. By the same token, it is free of frictionalengagement with the stem 14 and is, therefore, not subject to wear.

Communicating with the valve body 10, as by means of fittings 24, is aduct 26 connected to a suitable three-way valve 28, the valve in turnbeing connected through the bonnet 11 to a port 29 opening into thebottom of the recess 20. The valve 28 may include a pressure valveclosure plug 30 which normally closes off the duct 26 to the port 29 andnormally closed exhaust valve plug 32 which may be retracted to evacuatethe port 29 through the relief port 34.

In normal valve use, the seal ring 22 has no function and is completelyineffective as a seal, the stem packing l5 preventing any leakage ofpressure fluid from around the stem 14 and out through the bonnetopening 12. However, should it occur that the stern packing 15 or any ofthe O-rings 16 or I8 become damaged, it is highly desirable to be ableto replace the damaged parts without removing the valve from the line,or changing its setting, as by moving the valve to open position. Thiscan be accomplished by opening the main valve closure plug 30 topressurize the recess 20 behind the resilient seal 22 causing the sealring to contract circumferentially and snugly embrace the valve stem 14.With the seal ring squeezed between the sidewalls of the recess 20, thepressure so introduced cannot leak past the ring 22 and will beconcentrated fully on driving the ring radially inward to squeeze thestem to the position shown in FIG. 1A. Moreover, though the ring iscontracted circumferentially, its volume is not changed. Therefore, itscross section increases and squeezes more firmly across the recess 20.In any event, the pressure of fluid in the valve body 10 that risesaround the stem 14 will tend to squeeze the O-ring 22 against the upperwall of the recess 20 so that if there is any leakage of fluid from theport 29 past the ring 22, it will be around the bottom of the sealwhereby pressure from the duct 26 and the body pressure 10 will tend toequalize, squeezing the seal ring against the upper wall of the recessand around the stem to close off the clearance immediately above therecess 20.

While the resilient ring 22 is sealing ofl any leakage around the valvestem 14, the stem packing I5 may be removed as shown in FIG. IA, andrepaired or replaced. Thereafter, the packing 15 is replaced and thevalve plug 30 is closed to shut off any further flow through the duct26. Then, when the relief valve 32 is opened, the recess 20 will berelieved of pressure and the resilient ring 22 allowed to expand to itsnormal configuration out of contact with the stem 14.

The Embodiment of FIG. 2

Referring now to FIG. 2, there is shown a slightly modified embodimentwherein the resilient seal may be pressurized by attachment of ducts 26a 26 b to the upstream hub 10 a rather than to the body space as in theembodiment of FIG. 1. The duct 26 b is pressurized at 30, or exhaustedat 32, by operation ofa similar three-way valve 28.

The Embodiment of FIG. 3

In FIG. 3, there is shown a valve bonnet 38, 40 in which is carried astem packing 42 similar to that shown in FIG. I. The

stem 44 is carried within an enlarged opening 46 which insures free flowof fluid up to the stern packing for purpose to be described. In thisembodiment, a seal ring 48 is carried within a recess 50 and held inplace, as by means of a snapring 52. The seal ring 48 is normally out ofengagement with the valve stem 44 and is urged into the sealing positionshown only under circumstances to be described. A flow passage 54 isbored into the bonnet in a direction generally parallel to the enlargedclearance 46 and then through a lateral port 56 into the recess 50 abovethe seal ring. The passageway 54, 56 is normally open to providepressure equalization around the seal ring, but it may be closed bymeans of a suitable valve closure plug 58, which is threaded at 60 intothe valve bonnet 40. Also opening into the recess 50 above the seal ring48 is a vent valve 62.

in normal valve use of the embodiment of FIG. 3, the bypass valve 58 isopen and the relief valve 62 is closed to provide pressure equalizationaround the seal ring 48 so that it remains in its normal undeformedcondition out of engagement with the valve stem 44. However, when it isdesired to replace the stem packing 42, the bypass valve 58 is threadedinward in order to close off the passageway 54, and then the vent valveis opened to relieve the upper part of the recess of body pressure. Theresulting pressure differential across the seal ring 48 will cause it todeform upwardly into firm sealing engagement with the stem to permitremoval and replacement of the stem packing without leakage. After thepacking is replaced, the relief valve 62 is closed to shut off therecess to the atmosphere, and then the bypass valve 58 is opened toagain equalize the pressure around the auxiliary seal.

The Embodiment of FIG. 4

[n the embodiment of FIG. 4, there is provided a valve bonnet 66, 68accommodating a valve stem 70 through an opening 72 therethrough. A stempacking 74 normally seals ofi the clearance 72 against leakage from thebody interior. in a recess 76 below the stem packing, there is provideda channellike, resilient seal ring 78 and a perforated lantern ring 80supported on the bottom of the recess 72 between the flanges of thechannellike seal ring 76. The upper side of the recess is formed by aclamp ring 82, which is threaded into a complementary threaded opening84 in the bonnet 68 to squeeze the flanges of the resilient ring againstopposite sides of the perforated lantern ring 80. Hence, the channelmember forms an annular, hollow fluid vessel 76 a which is in directconnection with a port 86 through the perforations in the lantern ring80. A fluid passage 88 in communication with the port 86 carries apiston member 90 which is threaded at 92 into the duct 88. The duct 88is filled with a suitable liquid with a vent plug 94 removed to indicatewhen the filling is complete. Then, in normal valve operation with thefiller plug 94 and the piston member 90 in place, the fluid within thepassageway 88 is not pressured and the channel ring 76, being ofadiameter greater than that of the stem, performs no sealing function.However,

if it is desired to replace the stem packing 74, it is merely necessaryto thread the plug 92 inward to force the piston further into thepassageway 88 and drive the incompressible fluid under pressure into thechamber '76 0 within the seal, forcing the web of the channel memberinto snug sealing engagement with the stem.

While this invention has been described in conjunction with preferredembodiments, it is obvious that further modifications and changes may bemade thereto by those skilled in the art without departing from thespirit and scope of this invention.

What we claim is:

1. in a valve structure comprising:

a valve body housing having a bonnet with a generally cylindricalopening therein,

a complementary, generally cylindrical valve stem extending through saidopening, and

main packing means sealing off said opening around said valve stem,

An auxiliary yalve stem seal comprising: a recess in said bonnet aroundsaid valve stem inward of said main packing means,

a seal ring in said recess normally free of engagement with said valvestem but deformable under pressure differential in a given directionthereacross into sealing engagement around said valve stem;

duct means connecting said recess to said valve body housing forintroducing relatively high pressure fluid to said recess in said givendirection to produce said pressure differential, and

valve means selectively operated to block or free said duct means.

2. The combination defined by claim 1 wherein said recess has generallyparallel annular sidewalls and a bottom wall concentric with said valvestem, and said seal ring comprises:

an elastomeric ring contained in said recess,

said seal ring having an undeformed inner diameter larger than that ofsaid valve stem,

and said pressure fluid introducing means is selectively operated tobring the bottom of said recess into communication with a source of highpressure.

3. The combination defined by claim 1 including:

second duct means connecting said recess to atmosphere,

said valve means being operable to open said second duct means.

4. The combination defined by claim 2 wherein:

said seal ring normally seals between and against said recess sidewallsto prevent passage of pressure fluid introduced to the bottom of saidrecess.

5. The combination defined by claim 4 wherein:

said seal ring is normally of a cross-sectional dimension axi allythereof greater than the distance between said recess sidewalls.

1. In a valve structure comprising: a valve body housing having a bonnetwith a generally cylindrical opening therein, a complementary, generallycylindrical valve stem extending through said opening, and main packingmeans sealing off said opening around said valve stem, An auxiliaryvalve stem seal comprising: a recess in said bonnet around said valvestem inward of said main packing means, a seal ring in said recessnormally free of engagement with said valve stem but deformable underpressure differential in a given direction thereacross into sealingengagement around said valve stem; duct means connecting said recess tosaid valve body housing for introducing relatively high pressure fluidto said recess in said given direction to produce said pressuredifferential, and valve means selectively operated to block or free saidduct means.
 2. The combination defined by claim 1 wherein said recesshas generally parallel annular sidewalls and a bottom wall concentricwith said valve stem, and said seal ring comprises: an elastomeric ringcontained in said recess, said seal ring having an undeformed innerdiameter larger than that of said valve stem, and said pressure fluidintroducing means is selectively operated to bring the bottom of saidrecess into communication with a source of high pressure.
 3. Thecombination defined by claim 1 including: second duct means connectingsaid recess to atmosphere, said valve means being operable to open saidsecond duct means.
 4. The combination defined by claim 2 wherein: saidseal ring normally seals between and against said recess sidewalls toprevent passage of pressure fluid introduced to the bottom of saidrecess.
 5. The combination defined by claim 4 wherein: said seal ring isnormally of a cross-sectional dimension axially thereof greater than thedistance between said recess sidewalls.